Synthesis and bioactivity evaluation of novel spiromesifen derivatives

The development of environmentally friendly and novel structural pesticides is now an area of intense research in the agriculture field. Spirocyclic tetronic acids such as spiromesifen are typical compounds of this kind. In order to discover novel compounds with improved and broader-spectrum insecticidal activities, a series of spiromesifen derivatives were synthesised and bioassayed.

The derivatives were identified by (1) H NMR and MS. Preliminary bioassays demonstrated that some bioactivities of compounds 5a to 5u were better and had a broader spectrum than the lead compound spiromesifen. Moreover, these compounds showed better insecticidal activities against Mythimna sepatara and Aphis fabae than acaricidal activities against Tetranychus cinnabari. Furthermore, LC(50) of 5s against Aphis fabae reached 1.09 mg L(-1) . At the same time, compounds 5g, 5i, 5k and 5r also warrant further study because of their superior bioactivities to spiromesifen. What is more, suitable carbon chain length in the 4-position ester and the log P value of these spiromesifen derivatives dramatically influenced their insecticidal activities. Butyric or pentanoic ester and a log P value of 4.0-6.0 may be preferred.

The present work demonstrates that some spiromesifen derivatives can be used as potential lead compounds for developing novel insecticides and acaricides.